(1) Field of the Invention
The present invention relates to an aromatic polyamide film, in particular to a novel aromatic diaminoamide monomer, a high molecular weight aromatic polyamide produced by polymerizing the monomer, having high strength, high modulus, high viscosity and excellent heat-resistance, a high modulus aromatic polyamide film produced from the polymer and processes for production thereof.
(2) Description of the Prior Art
In general, aromatic polyamide films are used valuably in composite materials of air craft and automobile industry, building materials and leisure and sports goods because they have a light weight as well as high strength, high modulus, heat-resistance and abrasion resistance, and in some cases, insulating property.
Due to such utility, there have been developed various processes for producing polyamide film, including Kurihara et al.'s wherein polybenzoxazinone is reacted with ammonia or aniline to open the ring, thereby an aromatic polyamide having two amide substituents is obtained and then it is heat-treated to produce polyquinazolone which is a pure heterocyclic polymer [Polymer Journal Vol. 1, No. 4, pp 425-431 (1970)]. However, the heterocyclic polymer, polyquinazolone is so brittle that the products produced therefrom have poor endurance and abrasion resistance.
Japanese Patent Publication No. Sho. 57-17886 discloses a process wherein polyphenylene terephthalamide is dissolved in sulfuric acid to prepare an optical anisotropic liquid crystalline polymer and then it is discharged, converted to an isotropic polymer by the phase transition technique just before the coagulating bath and made into a film. This process includes the use of sulfuric acid which leads to difficulty in process control and occurrence of environmental contamination.
Japanese Patent laid-Open No. Sho. 51-81880 discloses a film making process wherein a polyphenylene terephthalamide derivative is prepared in order to use an organic solvent instead of sulfuric acid, thereafter the polymer is made into a film, which process has a drawback in that the film obtained has a poor heat-resistance and mechanical strength.